I don't remember the ages, but I know my daughter rolled over way faster than my son! She does everything a lot faster actually, except walking they both walked at 10 months.

Mine he is 21lbs!

About a month and a half from back to tummy and around 3 months from tummy to back.

My lazy butter ball hasnt done any of that! He hates being on his stomach let alone roll on his back! Hes 4 1/2 months! He will sometimes roll from his back to his side! But thats it hes pretty chubby maybe thats why....?

Around 3-4 months.

My daughter can go from back to stomach, but not stomach to back. Her pedi said that's weird because it's usually the other way around. But idk. she started at 4 mos.

Both of mine did the same at 3 months. Ped said that if they can roll themselves, then how they sleep is up to them. If they can roll they are developed enough to belly sleep if they choose. Just lay them down on their back, and if they roll they roll.

2 months from tummy to back and 4 months from back to tummy.

I agree with pp it's crib time.

And if she can roll back and forth then I wouldn't worry to much about it. Dd loves to sleep on her side and I don't feel to uncomfortable about that.

4-5 months. If she can roll from her stomach to her back it's generally fine to leave her to sleep on her tummy as she can lift her head to breathe. When my daughter would roll on her tummy to sleep Id keep rolling her back over as it made me nervous but there was no point because she would roll back over! She's 1 and still loves to sleep on her tummy.

Also, time to move to a crib if she is rolling :) more room